diff --git a/src/nostalgia/core/gfx.hpp b/src/nostalgia/core/gfx.hpp
index b171de9d..48c30af3 100644
--- a/src/nostalgia/core/gfx.hpp
+++ b/src/nostalgia/core/gfx.hpp
@@ -247,7 +247,11 @@ struct TileSheet {
 		const auto currentIdx = pIdx[pIdxIt];
 		if (pSubsheet->subsheets.size() <= currentIdx) {
 			auto out = pIdx;
-			out.back().value = pSubsheet->subsheets.size() - 1;
+			if (pSubsheet->subsheets.size()) {
+				out.back().value = pSubsheet->subsheets.size() - 1;
+			} else {
+				out.pop_back();
+			}
 			return out;
 		}
 		return validateSubSheetIdx(pIdx, pIdxIt + 1, &pSubsheet->subsheets[pIdx[pIdxIt]]);